The reserve requirement ratio is the amount of money the bank needs to hold at its account with one of the Federal Reserve Banks per dollar of deposits. A literal pile of cash would not count a single cent towards that requirement.

Modern requirements are based on core capital ratio, which is basically the ratio of a pile of cash that is set aside to deal with losses of assets as a fraction of the assets (weighted by risk, so, e.g., you don't need to set aside any money to protect against a literal pile of cash but you need lots of money to protect against a shitton of shitcoins).